The techniques described in JP2003-156130A and JP2005-325979A are well-known as conventional techniques for driving an oil pump. Specifically, a torque converter sleeve is provided so as to extend axially to an inner diameter side of an impeller shell that is coupled to a converter cover of a torque converter by welding or the like, and an engaging pawl is provided on an end portion of the torque converter sleeve.
The engaging pawl is inserted into an insertion hole provided in a side face of a drive sprocket supported on a transmission main body side, and transmits the driving force of an engine by contacting an inner side wall of the insertion hole.
A chain is looped around the drive sprocket (first sprocket) and a driven sprocket (second sprocket) supported on the oil pump side, and the chain transmits the rotation of the drive sprocket to the driven sprocket, whereby the oil pump is driven.
Typically, the converter cover is caused to expand by an oil temperature increase or oil pressure in the torque converter, and therefore slight axial movement of the torque converter sleeve must be permitted. For this purpose, an outer peripheral surface of the engaging pawl and an inner peripheral surface of the drive sprocket (insertion hole) are engaged to each other so as to be capable of axial movement, thereby permitting slight axial movement. Hence, the outer peripheral surface of the engaging pawl and the inner peripheral surface of the drive sprocket (insertion hole) are engaged to each other so as to be capable of axial movement, and therefore the driving force is transmitted while permitting axial movement.